What is the CVSS score of CVE-2026-52842?

CVE-2026-52842 has a CVSS 3.1 base score of 9.3 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N. EPSS exploitation probability: 0.2%.

Which versions of Lightpanda are affected by CVE-2026-52842?

Lightpanda headless browser versions before 0.3.1 contain a critical Same-Origin Policy bypass (CVSS 9.3) that allows attacker-controlled websites to impersonate arbitrary victim origins, breaking…. A patch is available.

How to fix or mitigate CVE-2026-52842?

Within 24 hours: audit all systems running Lightpanda to identify affected versions (any before 0.3.1) and map all business-critical automation pipelines using the tool. Within 7 days: implement interim mitigations by restricting Lightpanda-based automation to operate only on first-party origins and disabling cross-origin capabilities where possible; isolate affected systems on a segmented network with restricted outbound access to untrusted domains; and contact Lightpanda maintainers to confirm patch timeline. Within 30 days: prepare for immediate deployment of Lightpanda 0.3.1 or later once available, conduct regression testing of all affected automation workflows, and evaluate alternative headless browsers (Chromium headless, Puppeteer, Playwright) as contingency solutions.

Lightpanda CVE-2026-52842

EUVD-2026-44720 CRITICAL

Origin Validation Error (CWE-346)

2026-07-15 GitHub_M

Authentication Bypass Browser

9.3

CVSS 3.1 · Vendor: GitHub_M

Severity by source

Vendor (GitHub_M) PRIMARY

9.3 CRITICAL

AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N

vuln.today AI

9.3 CRITICAL

Remote, unauthenticated, low-complexity single crafted URL (AV:N/AC:L/PR:N) but needs the agent to visit it (UI:R); SOP bypass crosses origins (S:C) leaking and forging cross-origin data (C:H/I:H, A:N).

3.1 AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N

4.0 AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N

Primary rating from Vendor (GitHub_M).

CVSS VectorVendor: GitHub_M

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Changed

Confidentiality

High

Integrity

High

Availability

None

Lifecycle Timeline

Patch available

Jul 15, 2026 - 21:18 EUVD

Source Code Evidence Fetched

Jul 15, 2026 - 16:49 vuln.today

Analysis Generated

Jul 15, 2026 - 16:49 vuln.today

CVE Published

Jul 15, 2026 - 16:18 cve.org

CRITICAL 9.3

DescriptionCVE.org

Lightpanda is a headless browser designed for AI and automation. Prior to 0.3.1, Lightpanda searched for @ across the entire URL string instead of only the authority component when computing a page origin, so a URL such as http://attacker.com/@victim.com/ was fetched from attacker.com but treated as http://victim.com, allowing a complete Same-Origin Policy bypass. This issue is fixed in version 0.3.1.

AnalysisAI

Same-Origin Policy bypass in Lightpanda headless browser before 0.3.1 allows an attacker-controlled site to impersonate an arbitrary victim origin. Because origin computation searched for the '@' userinfo delimiter across the entire URL string rather than only the authority component, a URL like http://attacker.com/@victim.com/ was fetched from attacker.com yet treated as origin http://victim.com, breaking the fundamental web isolation boundary. No public exploit identified at time of analysis and not listed in CISA KEV, but the CVSS 9.3 rating and the trivial, deterministic nature of the parsing flaw make it a high-priority fix for any automation pipeline using Lightpanda.

Technical ContextAI

Lightpanda is a lightweight headless browser (written in Zig) purpose-built for AI agents, scraping and automation workloads as an alternative to Chromium-based headless setups. The flaw is a classic CWE-346 Origin Validation Error rooted in incorrect URL authority parsing: per RFC 3986 the userinfo '@' delimiter is only valid within the authority component (between '://' and the first '/', '?' or '#'), but the vulnerable getOrigin/getHost logic in src/browser/URL.zig used indexOf('@') over the whole raw string. Any '@' appearing later in the path was therefore misinterpreted as a userinfo separator, causing the host to be read from the path segment. The PR #1998 fix introduces a parseAuthority() helper that first bounds the authority to characters before '/?#' and only then searches for '@' inside that slice, and also hardens port/IPv6-bracket handling (e.g. [::1]:8080).

RemediationAI

Vendor-released patch: 0.3.1 - upgrade Lightpanda to version 0.3.1 or later, which replaces whole-string '@' searching with the bounded parseAuthority() logic (see release https://github.com/lightpanda-io/browser/releases/tag/0.3.1, PR https://github.com/lightpanda-io/browser/pull/1998, and advisory https://github.com/lightpanda-io/browser/security/advisories/GHSA-mq6p-m9cc-q432). If you cannot upgrade immediately, restrict the browser to trusted URLs only by validating or normalizing target URLs before handing them to Lightpanda and rejecting any URL whose path contains an '@' character before origin-sensitive operations; the trade-off is that legitimate URLs containing '@' in the path or query would also be blocked. Additionally, run automation jobs against untrusted content in isolated network segments or ephemeral sandboxes so a cross-origin data leak cannot reach sensitive internal resources, accepting the added infrastructure/latency overhead.